Insulation stripper of simprlified construction having improved safety features



June 7, 1966 A. s. APA ETAL 3,254,407

INSULATION STRIPPER OF SIMPLIFIED CONSTRUCTION HAVING IMPROVED SAFETY FEATURES Filed Jan. 13, 1964 2 Sheets-Sheet 1 [I] Z I \2 18 m I 7 q 5 A;

June 7, 1966 A. s. APA ETAL 3,254,407

INSULATION STRIPPER 0F SIMPLIFIED CONSTRUCTION HAVING IMPROVED SAFETY FEATURES 2 Sheets-Sheet 2 Filed Jan. 13, 1964 United States Patent 3,254,407 INSULATION STRIPPER 0F SIMPLIFIED CON- STRUCTION HAVING IMPROVED SAFETY FEATURES Armand Samuel Apa, Harrisburg, and Michael Francis OKeefe, Mechanicsburg, Pa., assignors to AMP Il1-' corporated, Harrisburg, Pa.

Filed Jan. 13, 1964, Ser. No. 337,303 1 Claim. (Cl. 3091) ing material surrounding the shielding. Quite frequently,

it is necessary to strip the insulation and a portion of the shielding material from the end of'a cable in 'a manner such that the inner conductor is exposed at the very end of the cable and a short portion of the shielding material is exposed adjacent to the end. For example, many types of commonly used connecting devices for coaxial cable require preparation of the ends in the manner described above. The stripping of the end of coaxial cable is quite often carried out by merely cutting away the necessary sections of the inner and outer conductors and the shielding by means of a pair of wire cutters and scissors, and the operation is usually a timeconsuming and costly one. When the end of a cable is stripped in the manner described above, the layer of shielding material, which is relatively thin, should not be damaged if the integrity of the cable and particularly the shielding material is to be maintained.

An object of the present invention is to provide an improved wire stripping device. A further object is to provide a stripping device for coaxial conductor which, in one operation, exposes the inner conductor of the cable and a portion of the shielding material. A further object is to provide a low cost and substantially foolproof stripping tool which avoids the possibility of damage to the cable when a stripping operation is carried out. A still further object is to provide a stripping tool having a minimum number of parts which can be produced at an extremely low cost without sacrificing of the precision of the cable stripping operation.

These and other objects of the invention are achieved in the preferred embodiment thereof comprising a frame block having a groove. extending thereacross and a blade housing arm pivotally mounted in the frame block. A pair of blades, which may be conventional razor blades, are mounted in spaced-apart slots in the blade arm in a manner such that the edges of the blades extend through a recess in the central portion of the arm and parallel to the groove in the frame block. An opening extends transversely of the groove through the frame block into which the end of the cable is inserted so that the cable extends transversely across the groove and normally of the planes of the blades in the blade arm. The two blades in the arm are positioned such that their edges are at different levels relative to the floor of the groove when the arm is in its lowered position, the one edge being at a location such that it cuts through the entire cable excepting the central conductor, and the other blade being disposed at a level such that it cuts only 3,254,407 Patented June 7, 1966 frame, lower the arm to cause the edges to cut into the cable, and rotate either the tool or the cable to produce a pair of spaced-apart circumferential cuts in the. end of the cable, one of the cuts extending into the cable to the central conductor and the other cut extending only through the outer insulating jacket or sheath. The arm is then raised, the cable is extracted from the opening and the undesired portions of insulation and braid material are removed from the end of the conductor.

In the drawing:

FIGURE 1 is a perspective view of a preferred form of insulation stripping device in accordance with the invention.

FIGURE 2 is sectional side view of the device of FIG- URE 1. FIGURE 3 is a side view similar to FIGURE 2 showing the blade arm in its lowered position.

FIGURE 4 is a sectional view taken along the lines 4-4 of FIGURE 3.

FIGURE 5 is a view taken along the lines 55 of FIGURE 3 FIGURE 6 is a perspective view of a short section of coaxial cable which has had its end stripped by means of the tool of FIGURE 1.

Referring first to FIGURE 6, a common form of coaxial cable comprises an inner metallic conductor 54, an inner sheath of insulating material 52 in surrounding relationship to the conductor 54, a sheath of metallic shielding material 50 which surrounds the insulating sheath 52, and finally an outer insulating sheath 48. When two separate cables of this type are to be spliced it is common to use any one of several types of connectors which connect both the inner conductors 54 and the shielding 50 of the two cables. The usage of such connectors quite frequently requires that ends of the cables be prepared as shown in FIGURE 6, that is With an exposed section of the inner conductor 54 at the end of the cable and with an adjacent exposed section of the shielding 50.- The embodiment of the invention described below is particularly intended to strip the end of a coaxial cable as shown in FIGURE 6 although alternative embodiments can be devised to strip the cable in alternative ways.

Referring now to FIGURES 1 and 2, the disclosed embodiment of the invention comprises a frame block 2 having a transversely extending groove 6 therein in which a blade arm 4 is pivotally mounted adjacent to its rearward end. The pivotal mounting of the blade arm is achieved by means of a roll pin 8 which extends through aligned openings in the frame block and in the blade arm. The pivotal axis of the blade arm is located such that when the arm is in its lowered or first position, the lower surface 10 of the blade arm is against the floor of the groove 6 of the frame as shown in FIGURE 3. The location of this pivotal axis and the shape of the right-hand side of the arm 4 is also such that the arm cannot be swung beyond its raised or second position as shown in FIGURE 2. Specifically, the rounded side 12 of the arm 4 has an increasing radius wit-h respect to the axis of pin 8 and this increasing radius is greater than the distance from the axis to the surface of the floor 7 of the groove. The rounded side 12 of the arm thus abuts the floor 7 after the limited pivotal movement illustrated in FIG- URES 2 and 3 has taken place and further upward movement of the arm is prevented.

A recess 14 extends transversely through the arm 4 on its underside parallel to the pivotal axis 8 of the arm and a pair of parallel slots 16, 18 extend inwardly from the rearward of the arm past the pivotal axis and intersect the recess. These slots are dimensioned to receive conventional injector type razor blades which are relatively long and narrow. The slots 16, 18 extend forwardly of the arm beyond the recess 14 as indicated at 20 and 22 so that after insertion of the blades, they are supported on each side of the recess 14 and their cutting edges are exposed and extend across the recess. It should be mentioned that the roll pin 8 extends through both of the slots 16, 18 and thereby functions to lock the blades in position after assembly. It will be noted from FIGURES 2 and 3 that the left-hand ends of the slots 16, 18 are closed so that the ends of the blades contained in the slots are protected and the technician using the tool cannot cut his fingers on the ends of the blades.

A pair of cylindrical openings 30, 32 extend through the frame block and intersect the groove 6. Since these openings are substantially, but not exactly, alike, at description of one will suflice for both and similar reference numerals, differentiated by prime marks, will be used for both of the openings. Thus the opening 30 comprises a conical lead-in section 34 on the left-hand side of the block as viewed in FIGURE 5 and a uniform diameter section 36 which extends to the groove 6 and is continued as shown at 40 on the right-hand side of the groove. The diameter of this uniform diameter section should be slightly greater than the outside diameter of the coaxial cable which is to be stripped so that the cable can be inserted into the opening, past the groove 6 until its end is disposed in the uniform diameter portion 40 of the opening and abuts a shoulder 44 formed by a reduced diameter section 42 on the right-hand side of the block. Advantageously, a trough 38 is provided on the floor 7 of the groove 6 in alignment with the opening, the radius of this trough being substantially equal to the radiu-s of the cable. The level of the openings 30, 32 relative to the floor 7 of the groove is such that an intermediate portion of the cable is supported in the groove after insertion.

The two blade receiving slots 16, 18 in the blade arm are parallel to each other but are offset vertically as viewed in FIGURE 4 so that the edge 26 of the blade 16 is at a lower level when the arm is in its lowered position than the edge 28 of the blade 18. The distance between the two blade edges will be dependent upon the precise size of cable being stripped and will be equal to the distance between the outer surface of the inner conductor 54 and the outer surface of the shielding material 50. The opening 30 is located relative to the groove 6 such that when a cable is positioned in the opening and the arm is in its lowered position (FIGURE 3), the edge 26 of the blade 16 will have cut through the cable up to the inner conductor and the blade 28 will have cut through only the outer insulating sheath 48 of the cable, that is up to, but not into, the shielding material 50.

In use, the blade arm is raised to the position shown at FIGURE 2, an end section of the cable is inserted into the opening 30 until its end abuts the shoulder 44, the blade arm is lowered and simultaneously either the tool or the cable is rotated to provide circumferential spaced apart cuts in the end of the cable, the one cut nearest to the end of the cable extending in the inner conductor 54 and the other cut extending to the shielding material 50. Thereafter, the arm is raised, the cable is withdrawn from the opening, and the severed sections of insulation are removed. As a practical matter, it is not desirable to attempt to dimension the parts such that the blade edge 26 cuts to the surface of the inner conductor 54 but rather to dimension the parts such that the edge of this blade will cut inwardly to a location adjacent to the surface. Similarly, the blade edge 28 should not cut inwardly to the surface of the shielding material but should cut substantially through the outer insulating sheath 48 to a position adjacent to this shielding material. If the parts are dimensioned to produce such cuts, which will deeply penetrate the cable as described above, it is merely necessary to lightly flex the end of a cable to cause complete severing of the insulating sheaths after which they can be axially slid from the end of the cable.

In the disclosed embodiment of the invention, the opening 32 is substantially similar to the opening 39 excepting that the shoulder 44' is located nearer to the righthand side of the groove 6 than is the shoulder 44. When a cable is stripped by inserting its end into the opening 30, a longer section of the inner conductor 54 will be exposed than is the case when the opening 32 is utilized.

As an alternative, it may be found desirable to dimension one of the openings for a diflerent size cable than the other and/or to provide more than two openings in the block.

Under some circumstances it is desirable to conically flare the braided shielding material 50 which is exposed adjacent to the end of the cable. This flaring operation can be facilitated by providing a recess 58 in surrounding relationship to the reduced diameter portion 42' of the opening 32, and forming a conical surface 56 on one side of this recess which surrounds the portion 42 of the opening. The opening 42 is formed with a diameter slightly'greater than the diameter of the inner sheath 52 of insulating material so that flaring of the shielding material can be accomplished by merely inserting the stripped end of the cable into the opening 42' and rotating it slowly during insertion. The circumferential surface 60 which surrounds the opening 42 will penetrate between the shielding material and the outer surface of the insulating sheath 52 so that as the cable is inserted into the opening 42', the shielding material will move over the conical surface 56 and be conically flared.

Some types of coaxial cable connectors require slightly different preparation of the end of the cable than that shown in FIGURE 6 in that it is required that the inner insulating sheath 52 extend beyond the end of the shielding material 50 but not to the end of the inner conductor 54. Stripping of the cable in this manner can be achieved in accordance with the invention by merely providing three slots in the blade arm rather than the two slots of the disclosed embodiment. The middle slot would be positioned such that the blade would cut entirely through the outer insulating sheath 48, through the braid material 50, but would not cut through the inner insulating sheath 52.

The frame housing and the blade arm of the disclosed embodiment are advantageously manufactured by molding process using any suitable plastic. The parts can be manufactured by an injection molding process using a suitable thermoplastic such as nylon. Alternatively, the parts can be manufactured by a compression molding process using a suitable thermosetting material such as phenolic resin. It will be apparent that an extremely low cost coaxial stripping device can be made by molding processes since all of the openings and slots can be produced in the molded part and no subsequent machining operations are required. Where this manufacturing technique is employed, a complete tool in accordance with the invention comprises only the molded frame block, the molded blade arm, and the roll pin 8. Molding processes are advantageous in that a high degree of dimensional precision can be obtained which is necessary to control the proper depth of cut for penetration of the two blades.

A distinct advantage of the disclosed form of the invention is that the cutting edges are at all times protected since the arm 4 can not be raised beyond the position of FIGURE 2. Furthermore, it is virtually impossible for the person using the tool to accidentally cut himself by virtue of this limitation of the movement of the arm 4.

It is apparent that a degree of adjustability as regards the length of the exposed section of shielding material 50 or the exposed section of the inner conductor 54 can be obtained, for example, by making the blade arm 4 in three parts which would be assembled in side-by-side relationship. One such part would contain a slot for the blade which is intended to cut through the insulating sheath 52 and the other part would contain a slot for the blade intended to cut only through the outer insulating sheath 48. The third part would be positioned between the two parts having slots and would function as a shim. The distance between these two blades could be varied to achieve varying lengths of exposed shielding material by interposing shims of different widths.

Change in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is olleredby way of illustration only. The actual scope of the invention is intended to be defined in the following claim when viewed in their proper perspective against the prior art.

We claim:

A device for stripping multi-layered cable to two diiferent levels comprising, a frame block having an opensided groove on one side thereof, a blade holder in said groove, a pair of side-by-side cutting blades in said blade holder having cutting edges extending'along the length of said blade holder, said blade holder having a pivotal mounting adjacent to one end thereof on an axis extending normally of said groove, stop means permitting limited pivotal movement of said blade holder between a first position in which said blade holder is seated in said groove and said cutting edges extend parallel to the floor of said groove and a second position in which said blade holder extends obliquely of the floor of said groove, said cutting edges being entirely between the sidewalls of said groove when said blade holder is in either of said positions, and a cylindrical opening extending through said block and normally of said groove, said opening intersecting said groove whereby, upon moving said blade holder to said second position and inserting said cable into said opening, and upon moving said blade holder to said first position, the insulation of said cable is penetrated by said blades to two different levels, and upon relative rotation of said block about the axis of said cable, said insulation is circumferentially cut to two different levels.

References Cited by the Examiner FOREIGN PATENTS 20 705,668 3/1954 Great Britain. 

